Machine gun



. 1934- c. E. SIMPSON 1,982,699

MACHINE GUN Filed May 8, 1934 2 Sheets-Sheet l Inventor Clarence E -Simpsnn EW i FWWZ Dec. 4, 1934. c. E. SIMPSON 1,982,699

' MACHINE GUN Filed May S, 1934 2 Sheets-Sheet 2 Inventor Clarence E-S'1Tn|:sun

E M/WW Attorney Patented Dec. 4, 1934 PATENT OFFICE MACHINE GUN Clarence E. Simpson, Springfield, Mass.

- Application May 8, 1934, Serial No. 724,523

6 Claims.

(Granted under the act of March 3, 1883, as amended April 30, 1928; 370 0. G. 757) The invention described herein may be manuiactured and used by or for the Government for governmental purposes, without the payment to me' of any royalty thereon.

- 6 Thisinvention relates to a machine gun.

The purpose of the invention is to provide means, readily applicable to existing machine guns; for regulating the rate of firing of the gun.

The invention is characterized by a piston whichlin its normalposition of rest does not interfere with the release of a sear but which when in movement opposes release of the sear. The pistonis arranged. to be retracted by the breech bolt but returns. independently at a regulated rate of speed to its initial position of rest. II Withthe foregoing and, other objects in view, the invention resides in "the novel arrangement and combination of parts and in the details of construction hereinafter described and claimed, it being understood that changes in the precise embodiment of the invention herein disclosed may be made within the scope of what is claimed without departing from'the spirit of the invention.

A practical embodiment of the invention is illustrated in the accompanying drawings,

whereim H Fig. 1 is a view in side elevation of the breech end of a machine gun equipped with the regulator and showingthe parts in position of rest.

Fig. 2.is a sectional view taken on the line 2--2 of Fig. 1 and showing the parts in full recoil withthe firing pin in cocked position.

Fig. 3 is a similar View showing the parts in position of rest'with the firing pin released by the sear.

Fig. 4 is a sectional view on the line 44 of Fig. 2 and showing thesear and sear slide in front elevation with the searheld by the slide.

' Fig. 5 is .aisimilar view on the line 5-5 of Fig. 3 and showing the .sear released. Flgt'fiis a group of detail views of the trigger bar- Fig. '7 is .a plan view, partly in section, of the .piston cylinder.

.slide. V

Fig. 14 is a group of detail views of the sear.

Fig. 15 is a sectional view on the line 15-15 of Fig. 12.

Fig. 16 is a view in end elevation of the rear cap of the cylinder. p

The invention is illustrated as applied to a machine gun of the Browning type in which a breech bolt 5 is mountedfor reciprocal movement in a breech casing 6. The bolt is provided with a firing pin 7 urged forwardly by a spring 8 and retracted by a cocking lever 9 during recoil of the bolt.

The firing pin is held in cocked position by a sear mechanism which is generally similarto that shown in Patent No. 1,803,350 of May 5, 1931. The firing pin is formed with a recess 10 in one side adjacent its rear end for receiving a finger 11 projecting from the front face of a sear 12. The rear face 13 of the recess and the rear face 14 of the finger are mutually inclined to form cam surfaces whereby the finger is capable of being cammedout of the recess 10 and disengaged from the firing pin when the firing pin moves forwardly under the influence of its spring 8. When the finger is out of the recess 10 as seen in Fig. 3 it rests on a shelf 15 on the rear end of the firing pin. The shelf 15 passes through an aperture 12a in the sear.

The sear is mounted in the bolt for movement horizontally thereof and is held in locked engagement with the firing pin by means of a slide 16 mounted in the bolt for vertical movement. A lug 17 on the front face of the vertical slide 16 is adapted to enter a recess 18 in the upper edge of the sear, which recess is duplicated in the lower edge as at 18a whereby the sear is reversible to permit right or left hand operation as is well understood in the art.

One end of the recess 18 is formed with an abrupt shoulder 19 which is engaged by the lug 17 (Fig. 4) when the finger 11 of the sear is within the recess 10 of the firing pin (Fig. 2). In this arrangement of the parts, the slide 16 through its lug 17 positively locks the sear in position to hold the firing pin cocked. A plunger 26 carried in one end of the sear and acting against a rib 21 on the slide normally urges the sear towards the locking position. A plunger 22 carried in the upper end of the slide and seated on a bar 23 carried by the bolt normally depresses the slide into engagement with the sear. The slide is elevated against the action of the plunger 22 by a trigger 24. An aperture 16a is provided in the slide 16 to permit passage of the shelf 15 0f the firing pin.

A handle 25 carried by the bolt and provided for manual retraction thereof, rides in slots 26 and 27 (Fig. 5) respectively formed in the right and left side plates of the breech casing 6. This handle is similar to the conventional handle of the Browning gun except that it is longer and preferably projects beyond both side plates of the casing. v I

The mechanism for regulating the speed of firing is shown mounted on the left side of the breech casing although it may also be mounted on the right side. It comprises a cylinder 28 whose ends are closed by a rear cap 29 and a front cap 30. The caps are preferably provided with means for mounting them on the breech casing and to this end the cap 29 has brackets 31-31 and a key 32 and the cap 30 has a bracket 33 and keys 34. The brackets are secured to th breech casing by screws 35. 1

The rear cap 29 is provided with a relatively large vent 36 while the front cap has a small vent 37 leading towards an outlet 37a and controlled by a needle valve 38. The valve is threadedly mounted in the front cap and has a thumb-wheel 39 formed peripherally with recesses 40 for engagement of a click lath 41.

Within the cylinder 28 there is a tubular piston 42 having a radially projecting finger 43 extending through a slot 44 in the cylinder and disposed in the path of movement of the bolt handle 25. The piston is formed with a closed front end 45 and is normally held in the forward position by a helical spring 46 confined between the front end and a disc 4'? on the rear end of a guide rod 48. The disc 4'1 has a lug 49 inserted in the slot 44 of the cylinder.

The piston is provided adjacent its rear end with a recess 50 whose front wall is inclined to constitute a cam surface 51. A trip bar 52 pivotally mounted on a pin 53 passing through spaced ears 54-54 on the cylinder is disposed in an aperture 55 in the side plate of the breechcasing. The free'end of the trip bar is formed into a. headwhose inner portion 56 is adapted to engage the sear 12 of the breech bolt when the bolt is in battery and whose outer portion 5'7 is adapted to move through an aperture 58 in the cylinder and enter the recess 50 in the piston.

The cylinder 28 is provided with an air inlet 59 (Fig. 2) which is positioned just forwardly of the front end of the piston 42 when the piston is in retracted position.

In the normal position of the parts shown in Figs. 3 and 5 the trip bar 52 is free to be swun about its pivot and does not oppose movement of the sear 12 which is free to be moved in releasing the firing pin. When the gun is fired, the breech bolt moves in recoil and during the intermediate portion of its stroke the bolt handle 25 engages the finger 43 of the piston 42 and retracts the piston against the action of the spring 46 (Figs. 2 and-4). The trip bar 52 is forced out of the recess 50 of the piston and is swung inwardly where it is held by the piston so long as the piston is out of its forward or in battery position.

When thetrip bar 52 is held in the inward position, the inner portion 56 of its head will prevent lateral movement of the sear 12 even though the slide 16 has been actuated by the trigger 24, to release the sear as the breech bolt arrives in battery. Therefore the sear cannot be released until the piston 42 returns to its forward position and brings its recess 50 into alignment with the outer portion 57 of the head of the trip bar.

While the breech bolt, after completion of its 'of fire of the gun is desired the vent 37 is wide open so that the piston is practically unopposed and will arrive in battery simutlaneously with the breech bolt. The rate of fire is controlled by adjusting the valve to regulate the effective opening of the vent.

I claim.

1. In a gun, a breech casing, a reclproca breech bolt in the casing, a handle on the bolt, a sear carried by the bolt, a cylinder on the breech casing, a vent in the front end of the cylinder, a valve for controlling the effective opening'of the vent, a piston in the cylinder and including a finger disposed in the path of recoil movement of the bolt handle, a spring normally holding the piston in the front portion of the cylinder, said piston having a recess with a front cam wall, a trip bar pivotally carried by the cylinder and having its free-end movable between the breech bolt and the piston and engageable therewith, said bar held by the piston in the path of movement of the sear and receivable in the recess of the piston when the piston is in forward position to free the sear.

2. In a gun, a breech casing, a reciprocable breech bolt in the casing, a handle on the bolt, a sear carried by the bolt, a cylinder on the breech casing, a vent in the front end of the cylinder, a valve for controlling the effective opening of the vent, a piston in the cylinder and including a finger disposed in the path of recoil movement of the bolt handle, a spring normally holding the piston in the front portion of the cylinder, said piston having a recess with a front cam wall, a member movable between the breech bolt and piston and engageable therewith, said member held by the piston in the path of movement of the sear and receivable in the recess of the piston when the piston is in forward position to free the sear.

3. In a gun, a breech casing, a reciprocable breech bolt in the casing, a sear carried by the bolt, a cylinder on the breech casing, a vent in the front end of the cylinder, a valve for controlling the effective opening of the vent, a piston in the cylinder, means for normally holding the piston in the front portion of the cylinder, 8 connection between the breech bolt and piston whereby the piston is retracted by the breech bolt, and a member movable between the breech bolt and piston and held by the piston in the path of movement 01 the sear when the piston is out of its forward position.

4. In a gun,.a'breech casing, a reciprocable breech bolt in the casing, a sear carried bysthe bolt, a cylinder on the breech casing, a piston in the cylinder, means for normally holding the piston in the front portion of the cylinder, a connection between the breech bolt and piston whereby the piston is retracted by the breech bolt, means for controlling the speed of return of the piston, a member movable between the breech bolt and piston and held by the piston in the path of movement of the sear when the piston is out of its position'of rest. I

5. In a gun, a breech casing, a reciprocable breech bolt in the casing, a sear carried by the bolt, a member movable transversely of the easing, a member reciprocable longitudinally of the casing and during its reciprocation holding the transversely movable member in the path of the sear, and means for controlling the rate of movement of the reciprocable member.

6. In a gun, a breech casing, a reciprocable 

